The Study On Biomarkers Of Susceptibility And DNA Adduct Characteristics Of Formaldehyde

There has been one severe problem about public health that people are exposed to formaldehyde (FA). FA could damage immune system, respiratory system, nerve system, cardiovascular system and organs such as skin and liver etc. High concentration of formaldehyde has genetoxic. In the year of 2004, IARC identified it as a groupⅠcarcinogen.It belongs to volatile organic chemicals with a boiling point at -19℃and is easy to volatilize at indoor temperature. Formaldehyde is micromolecule aldehyde chemical compound that has electropositivity and vivid chemical property. It can attack nucleophilic group and result in the damage of giant molecular substance such as protein, nucleic acid.Along with the rapid development of theory and technology of molecular biology, the study of biomarker, a brand-new field, has gradually drawn attention in the field of phylaxiology throughout the world. What biomarker reflecting is the molecular changes of physiology, biochemical, immunity and heredity, etc. These changes are evoked by the interaction of biosystem and environmental factors-chemical, physical and biological factors. Biomarker is an important milestone that manifest environmental medicine has developed at molecular level.The research about it has vital value in the field of molecular epidemiology, molecular toxicology, labour hygiene, environmental medicine, etc.DNA adduct, a biomarker of biological effective dose ( target dosage), is formed while toxic compounds enter a human body and interact with DNA. DNA adduct may become the minimum factor to lead to "three results"(cancer, malformationl, mutation)once it escapes the procedure of DNA repair.Biomarkers of susceptibility indicate the reaction ability to exogenous compound metabolism, for example, people lack ofα-1-antitrypsin get emphysema pulmonum when contact respiratory stimulants. Genetic polymorphism is an important type of biomarker. Different morphous of metabolic enzyme has different response during the procedure of exogenous compounds have toxic effect on organism and determines reaction ability of organism to chemical intoxicant. As a result, it can be taken as an important screening index to occupational contraindication. American National Institute for Environmental Health Science (NIEHS) and China commenced Environmental Genomic Project (EGP) to explore the interaction and search for the relationship between susceptible genetic polymorphisms and diseases with the methods that HGP (human genome project) used.The study on genetic polymorphisms is vital in the future in occupational diseases prevention. It can discuss the mechanism of intoxicant action on the molecular level, and accelerate assessing reaction nature of intoxicant, and screen high risk people group, etc.【Objective】1. We approach to the chemical characteristics of DNA adducts formed by formaldehyde in vitro testing system and determine whether DNA adducts lied in human cells curtured in vitro contaminated by formaldehyde on the molecular level, and offer scientific theoretical basis for biological monitoring, precaution, and evaluation of the risk of population group exposed to formaldehyde.2. The project can offer scientific theoretical basis for screening occupational people and monitoring health of high risk group to protect the health of FA exposed population group and help to strengthen the primary prevention through exploring the relationship between genetic polymorphisms and the susceptibility of FA metabolism, and searching for the susceptible biomarkers of FA occupational hazard on the base of molecular epidemiology. The results will bring significant social benefits and economic returns.【Contents】 1. We applied the method of culturing in vitro and analyses with HPLC to study the chemical damage mechanism of formaldehyde, including the formation of DNA adduct, the biding site of DNA, the type of the chemical linkage of DNA adduct and the order of addition reaction, et al.2. In the vitro model of cell contaminated by formaldehyde, we adopted the method of UV absorption spectrum shift to approach the characteristics of the DNA addition reaction of formaldehyde in lymphocytes,and then conformed that it can form DNA adducts in human lymphocytes,which is harmful to mammalian cells in a certain degree.3. 107 occupational contact person of formaldehyde were included in the cross sectioning epidemiologic study. We applied the method of PCR-RFLP to monitor the gene polymorphisms of ALDH2 and CYP2E1, and we monitored the exposure dose and the content of formic acid in post-work urine, and statistically analysed the influence of gene polymorphisms on the metabolism of formaldehyde.【Results】1. In vitro model system, one molecular of formaldehyde and one molecular of dAMP form stable adduct through covalent bond.2. Health people peripheral blood lymphocytes contaminated by formaldehyde indicated that active CHO- contained in formaldehyde made them directly attack nucleate base in vitro cell culture. When 40μmol/L, formaldehyde can weakly bind with human lymphocytes DNA. When >40μmol/L, formaldehyde easily bind with human lymphocytes DNA, in accordance with the report that formaldehyde bind with calf thymus DNA in vitro testing, which manifested that formaldehyde was one genetoxin.3. Detecting the genotype of ALDH2 and CYP2E1 of 107 workers exposed to formaldehyde through collecting peripheral blood lymphocytes, we can find the level of urine formic acid increment was influenced by genotypes of ALDH2(Kruskal Wallisχ2=9.241, P<0.05).The metabolism of ALDH2 *1 homozygotic genotype to formaldehyde is more active than ALDH2 *2 homozygotic genotype(the difference of the two mean rank is 13.30), but the polymorphism of Rsa I/Pst I site of CYP2E1 5`-franking region Rsa I/Pst I site did not influence the level of urine formic acid increments (χ2=4.285,P>0.05). Genotypes of ALDH2 were related to susceptibility to the metabolism of formaldehyde in human. So ALDH2 can be taken as formaldehyde susceptible biomarker, can be used to screen formaldehyde occupational contraindication.【Conclusion】1. One molecular of formaldehyde and one molecular of dAMP can form stable adduct through covalent bond.2. Health people peripheral lymphocytes contaminated by formaldehyde indicated that formaldehyde could induce addition reaction with DNA in vitro cell culture.3. Gene polymorphisms of ALDH2 affected the metabolism process of FA, while genotypes of CYP2E1 were not related with FA metabolites through statistical analysis.